Final answer:
To solve the problem, set up a proportion using the given information and solve for the unknown travel time when driving.
Step-by-step explanation:
To solve this problem, we need to set up a proportion using the given information. Let's assume Greg's travel time when walking is represented by x minutes, his travel time when riding his bike is represented by y minutes, and his travel time when driving is represented by z minutes. We can set up the proportion:
x : y = y : z
Since the ratio of Greg's travel times is proportional, we can write the equation:
x/y = y/z
Now, we can solve for z by cross-multiplying and simplifying the equation:
x*z = y*y
z = (y*y)/x
Since the problem does not provide specific values for x and y, we cannot determine the exact value of z. Therefore, we cannot provide a specific answer to this question.